[Objective] This study determines the statistical characteristics of the distribution of valleys in East Gansu Province in order to ascertain the macroscopic valley evolution in the Loess Plateau.[Methods] Field work, previous data, and remote sensing were combined to determine the distribution of loess gullies in the study region. Then, based on the classification of valleys and gullies using data processing, the expression of parameters was quantified for determining gulch development, performed statistical tests, characterized the normal distribution, and statistical tests and normal distribution properties were used to obtain the influence relationship between valleys, and cited concept parameters (e.g., safe distance), to reproduce and predict the geomorphic evolutionary process.[Results] ① There was an almost orthogonal relationship between the main trench and branch trench. The joint trend was roughly the same as that of the branch trench, and the structure controlled the development of the trench. ② The radian value data of the orthogonal deviation between the primary branch and main branch of the four groups, and the secondary branch and primary branch of the two groups all conformed to a normal distribution. ③ At a significant probability of 80%, the included angles between the main trench and first branch trench should be ≥ 69.9°, 67.6°, 59.9°, and 68.8°. The included angle between the primary and secondary branches was ≥ 55.8° and 70.5°.[Conclusion] There is a universal law in the development of valleys, whereby 70° can be regarded as the limit value of the angle of gully development.